The present invention generally concerns the control of light transmissions to generate desired light patterns and is specifically directed to a programmable matrix device which employs individually electrically energizable cells in a planar matrix array to effectuate such control.
There appears to be a substantial need for new and innovative programmable light control devices to control light transmissions for generating desired light patterns. A pregnant example of one application should help underscore this need.
As is well known, photographic masks are used to make image reproductions in quantity by generating permanent images on a photosensitive surface through the control of light which impinges thereon. Chemical reactions in the photosensitive coating of the surface produced by the light pattern striking it via the mask produces a permanent visual record of the light pattern. In the case of two-tone images, the mask contains in the form of artwork on a substrate of mylar or equivalent a combination of transparent and opaque areas for respectively completely passing and blocking light which defines the desired pattern. Because of the permanency of the artwork on the substrate, once the mask has served its purpose it cannot be reused for other patterns despite all of the time, effort and expense required to generate it in the first place.
There are numerous applications to which photographic masks are put. For example, in the manufacture of printed circuit boards one of the first steps is to either polymerize or degrade the polymerization, dependent upon whether a positive or negative process is used, of a photoresist material coated on the board which then permits the affected exposed areas of underlying copper substrate to be etched away thereafter. This step of polymerization is carried out by directing light, in particular ultra-violet rays, on the photoresist surface through a mask containing the desired pattern.
Because of the types of applications to which photographic masks are put, printed circuit boards being one example thereof, the art work used for producing the pattern of the mask requires a great degree of precision and accuracy to achieve a high degree of image resolution. Accordingly, these masks are normally produced through very sophisticated and expensive numerically controlled machines having a moving head which can be precisely positioned in the X-Y plane for directing light to generate the mask. The requisite machine movement not only adds to the production time for generating a photographic mask but also necessitates greater maintenance and repair periods which adds to the operating costs of the machine and detracts from its availability. In view of the large capital investment for these machines, the maintenance and repair downtimes represent an important factor in the manufacture of photographic masks. If the machine movement giving rise to the added maintenance and repair record could be eliminated, considerable savings would be realized. Although it may appear that the problem of reusable masks could be obviated by simply applying the machine controlled light directly to the photosensitive surface bearing the pattern reproduction, thereby eliminating the mask altogether, this is not a viable business alternative because of the large capitalized cost of the machine and its relatively slow operation, particularly in view of the large quantity of reproductions required.
With the foregoing example in mind, it is a primary object of the present invention to provide a new and innovative light control device, in the form of a planar matrix array of individually electrically energizable cells, which is programmable so that it can be reused as often as desired to generate different light patterns and entails no movement of components.
It is a further object of the present invention to provide such a programmable light control matrix device which may be easily fabricated and yet affords a high degree of image resolution.
These, as well as other objects and the means by which they are attained through the present invention, may be fully appreciated by referring to the Detailed Description of the Invention which follows hereinbelow together with the appended drawings.